1. Field of the Invention
The subject invention is directed to cardiac leads, and more particularly, to passive and active unipolar, bipolar, tripolar and quadrupolar endocardial stimulation leads that are adapted and configured to elute a steroid to treat cardiac tissue.
2. Background of the Related Art
Implantable cardiac stimulation leads, including endocardial leads, are well known in the art. In general, these devices have an elongated flexible body with an electrode at one end for contacting cardiac tissue and a connector at the other end for mating with an automated stimulation device, namely a pacemaker or defibrillator. The electrode of an endocardial lead may be secured within a chamber of the heart by passive fixation through the use of a plurality of flexible tines which project outwardly from the end of the lead body, or by active fixation through the use of a helical fixation screw.
When an endocardial lead has been implanted in the heart, either by active or passive fixation, it has been determined that the cardiac tissue at the site of implantation will react favorably to the lead in the presence of a therapeutic drug, such as, for example, a steroid. Consequently, cardiac leads have been designed with means for delivering a therapeutic drug to the cardiac tissue at the implantation site.
One such example of a lead having drug delivery means is disclosed in U.S. Pat. No. 5,902,330 to Ollivier et al. which describes a pacing lead having a frusto-conical diffusion ring fixed in place by gluing. The diffusion ring is constructed of porous silicone and loaded with an active material, such as a steroid, for distributing the steroid in the region of the myocardium adjacent the electrode. Another example of a drug delivery device is disclosed in U.S. Pat. No. 6,361,780 to Ley et al. which describes a microporous bio-compatible collar or annulus having a therapeutic drug within its pores. The collar or annulus is preferably formed from a ceramic material and is designed to surround a portion of a lead or catheter.